Tube drawing machines



6, 1969 s. H. RICHARDS ETAL 3,462,992 I TUBE DRAWING MACHINES 4 sheets-sheet 1 Filed Sept. 14, 1966 INVENTORS SAMUEL H. RICHARDS NORMAN D. BENSON BYZM ATTORNEYS 26, 1969 I s. H. RICHARDS ETAL 3,462,992

TUBE DRAWING MACHINES Filed Sept. 14. 1966 4 Sheets-Sheet 2 F IGJB.

4 Sheets-Sheet 5 5. H. RICHARDS ETAL Aug. 26, 1969 TUBE DRAWING MACHINES Filed Sept. 14, 1966 26, 1969 s. H. RICHARDS ETAL 3,462,992

TUBE DRAWING MACHINES 4 Sheets-Sheet 4 Filed Sept. 14. 1966 QNGE United States Patent US. Cl. 72-280 6 Claims ABSTRACT OF THE DISCLOSURE A tube drawing machine having a drawing block, a

spool on each side of the drawing block which alternately functions as a pay-out reel and a take-up reel and dies between the drawing block and spools in alignment with tangents to diametrically opposed points on the surface of the drawing block. The drawing block is rotated in one angular direction and is selectively operable for drawing tubing through each of the dies from one of the spools, which thereby functions as the pay-out reel, onto the other spool, which thereby functions as the take-up reel.

This invention relates to an improved method of drawing metal tubing and also to an improved tube drawing machine.

In the drawing of metal tubing, there are advantages which result from operating with coils of tubing which are as long as possible since, the longer a coil of tubing is, the smaller the proportion of the total drawing time of a coil, is taken up by the coil end preparation (i.e. lubricating, inserting the floating plug into and pointing the tube end, threading the pointed end through the die and securing the pointed end to the drawing block). In general therefore, for economical operation of a tube drawing machine, it is preferable to design the machine so that coils can be employed whose size is limited only by considerations of the ease of handling.

In the case of coils of large bore diameter tubing the acceptable limit to ease of handing is normally set by the overall weight of the coil and in the case of coils of small bore diameter tubing the acceptable limit is often set by the problems involved in controlling the many turns of tubing in a long coil without running the risk of tangling the turns or otherwise damaging the tubing.

In the specification of United States application No. 403,607, now Patent No. 3,330,146, a tube drawing machine is described in which the rotatable drawing block is interposed between coil-supporting spools so that a long coil of tubing on one spool may be drawn through a die onto the block and taken-up on a further spool, so that the entire length of the coil is supported on a spool, except for the short length between the spools, a part of which is coiled around the block.

In the operation of the machine described in the aforementioned specification, the direction of rotation of the block is reversed for each successive drawing operation to which a given coil is subjected, so that it is the same longitudinal fibres of the tubing which each time form the circle of maximum circumference when the coil is drawn onto the block. It is known that the fibres of the tubing forming the outside surface of the turns on the block are subjected to greater stress during drawing than the fibres forming that surface of the turns which is in contact with the surface of the block, and there is reason to believe that the practice of drawing tube so that the same fibres are always subjected to the maximum stress, produces a less uniform tubing.

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This invention relates to a modification of the machine described in the aforementioned specification which embodies the advantages of that machine and which also permits the stresses imposed during drawing to be more uniformly distributed throughout the fibres of the tubing.

According to one aspect of the present invention, a method of drawing metal tubing comprises leading a coil of tubing from a rotating paying-out spool through a drawing die, laying the tubing as it leaves the die, in a helix on the surface of a drawing block rotating in one direction, and collecting the tubing as it leaves the block as a coil on a rotating take-up spool, said take-up spool subsequently serving as the paying-out spool when, in a later operation the tubing is drawn in the opposite direction through a further die by the drawing block again rotating in said one direction.

Conveniently the helix of tubing on the block would consist of between 4 and 8 turns. Preferably the speeds of rotation of the two spools and the block are controlled so that tension is maintained in the tubing in the length extending between the paying-out spool and the die and in the length extending between the block and the take-up spool.

According to a further aspect of the present invention a tube drawing machine comprises a rotatable drawing block having a tube-engaging peripheral surface which is symmetrical about a vertical axis of rotation of the block, a first spool-supporting member and a first die disposed on one side of a vertical plane through the axis of rotation of the block, and a second spool-supporting member and a second die disposed on the opposite side of said plane, the axis of one of said dies being collinear with the tangent to the tube-engaging surface of the block at a first point and the axis of the other die being collinear with the tangent to the tube-engaging surface of the block at a second point which is spaced around the periphery of the block relative to said first point.

Preferably said die axes are parallel, the first and second points being diametrically disposed relative to the block.

If desired, more than one pair of spool-supporting members and associated dies may be provided so that a coil on one supporting member of one pair may be prepared for drawing while a coil is being drawn between the supporting members of the other pair.

Preferably, to facilitate layering of a coil as it is wound onto a spool mounted on a supporting member, each supporting member is arranged for reciprocation in a vertical direction.

One form of tube drawing machine in accordance with the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:

FIGURES 1A and 1B are a plan of the machine, and FIGURES 2A and 2B are side elevation of the machine of FIGURES 1A and 1B.

The tube drawing machine illustrated comprises a drawing block 1 mounted to rotate about a vertical axis and having a cylindrical tube-engaging peripheral surface 2. Two vertically mounted, rotatable, spool-supporting members 3 and 4 are located on opposite sides of a vertical plane through the axis of rotation of the block 1, the rotating axes of the members) and 4 lying in a vertical plane containing the rotational axis of the block 1. The spool-supporting members 3 and 4 each embody an hydraulically operated expanding mandrel on which tube spools 5 and 6, respectively, are located. Intermediate each member 3 and 4 and the block 1 is a die box 7 and 8, respectively, the die boxes being positioned so that the drafting axes of dies contained therein are parallel and form tangents to the surface 2 at diametrically opposite points on the surface 2. Each die box is mounted on a carriage 7a and 8a, respectively, each carriage being movable in a vertical direction for a purpose hereinafter more fully to be specified.

Associated with the block 1 is a powered pulling-in dog, 9, a plurality of hold-down rolls 10 and a tiltable fleeting ring 11. Associated with each spool-supporting members 3 and 4 is a cluster of bending rolls 12, a traverse control mechanism 13 and a tube-guiding trough 14.

The machine would be operated in the following manner:

A coil of tubing from a. conventional tube drawing machine would be employed and would be fed to the machine from a swift.

After lubricating, inserting a floating plug and pointing, the end of a coil of tubing resting on a conventional swift (not shown but located to the left of the block 1) is passed through a die in the die box 7, secured to dog 9 and drawn on to the block 1.

The dog 9 is shown in FIGURE 1 in its extended position (in which it can engage the end of tubing as it passes through the die) but during a drawing operation is located in a recess close to the upper end of the block 1. To lay the initial turns on the block, the carriage 7a and die box 7 are moved slowly downards as the block is rotated, the rate of lowering of the box 7 being determined on the basis of the external diameter of the tubing and the speed of rotation of the block so that the tubing forms a smooth helix on the surface 2. When the tubing reaches the fleeting ring 11 (usually after about 4 or 6 turns have been drawn on to the block), the block is stopped and the end of tubing gripped in the dog 9 is cut off. Slow rotation of the block is now continued again and the free end of the drawn tubing is moved along the right hand trough 14 and, after being passed through the bending rolls 12, is secured to the spool 6. During this latter operation of feeding tubing to the spool 6, the die box 7 is maintained in its low position so that as freshly drawn tubing is laid on the block in the tapering gap between the last turn already on the block and the inclined fleeting ring 11, it urges the turns already on the block 1 upwardly towards the top of the block.

The machine is now ready for normal operation, and the block 1 can be rotated at high speed to draw the entire coil of tubing on the swift through the die and on to the spool 6. The spool 6 is rotated throughout at a speed sufficient to maintain some tension in the tubing passing through the trough 14. As drawing proceeds, the spool 6 is reciprocated vertically to layer the tubing in a neat coil between the spool flanges.

The hold-down rolls 10 urge the turns against the block during the threading-up procedure but may be withdrawn from the tubing when the machine is operating at speed.

The tubing is next passed from spool 6 to spool via die box 8 with the threading-up of the machine being carried out exactly as previously described. Since the tubing is now approaching the block 1 from right to left (as opposed to left to right in the previous operation) the inclination of the fleeting ring 11 must be changed to provide the desired upward movement of the turns on the block during drawing.

The coil is passed from one spool to the other through a series of dies until the entire series of drawing operations on the coil is completed.

From what has been said, it will be appreciated that since the direction of rotation of the block 1 remains the same throughout, the longitudinal fibres of the tube lying in that region of the cross-section of the tube which is radially outermost when the tubing is wrapped round the block 1 during one drawing operation will lie in the region in contact with the block 1 during the next drawing operation. In this way the maximum stresses occasioned by drawing are shared between fibres of the tube in diametrically opposite regions of the cross-section of the tube, so that the stresses imposed during drawing are more uniformly distributed throughout the fibres of the tubing.

Although the specific machine illustrated employs just two spool-supporting members and two die boxes, it will be appreciated that advantages are obtained by working with more than one opposed pair of spool-supporting members, since in this way coil-end preparation may be carried out on a coil on one spool of one pair of spools, while drawing is being carried out on a coil supported between another pair of spools.

Although we prefer to reciprocate the spool-supporting members to achieve layering of a coil on a spool, it will be appreciated that a similar effect may be achieved by moving the tubing up and down relative to a spool rotating at a constant height.

In the specific description given above it is mentioned that the block 1 is stopped during severance of the tube end from the dog 9 and restarted when tubing is being led to the appropriate spool. In practice, provided the block 1 is equipped with cutting means for automatically severing the tube end, at the appropriate moment, the threading up operation can be completed without stopping the block at all, the tube end being taken, as it springs away from the block on severance from the dog, and led along the trough 14.

The hold-down rolls 10 may be employed during the final stage of the drawing operation on a tube coil, to prevent the end of the tube flying from the block surface when drawing tension is released.

In FIGURES 1A and 1B of the drawings, the approximate path taken by tubing when approaching the block 1 is shown in full lines while the approximate path taken by tubing leaving the block has been shown in broken lines.

We claim:

1. A method of drawing metal tubing comprising leading a coil of tubing from a rotating paying-out spool through a first drawing die, laying the tubing as it leaves the die, in a helix on the surface of a drawing block rotating in one direction, and collecting the tubing as it leaves the block as a coil on a rotating take-up spool located on the other side, relative to said paying-out spool, of a vertical plane containing the axis of the block, said take-up spool subsequently serving as the paying-out spool when, in a later operation the tubing is drawn in the opposite direction through a further die mounted, relative to said first die, on the other side of said plane by the drawing block again rotating in said one direction.

2. A method as claimed in claim 1, in which the helix of tubing on the block consists of between 4 and 8 turns.

3. A method as claimed in claim 1 or claim 2, in which the speeds of rotation of the two spools and the block are controlled so that tension is maintained in the tubing in the length extending between the paying-out spool and the die and in the length extending between the block and the take-up spool.

4. A tube drawing machine comprising a rotatable drawing block having a tube-engaging peripheral surface which is symmetrical about a vertical axis of rotation of the block, a first spool-supporting member and a first die disposed on one side of a vertical plane through the axis of rotation of the block, and a second spool-supporting member and a second die disposed on the opposite side of said plane, the axis of one of said dies being collinear with the tangent to the tube-engaging surface of the block at a first point and the axis of the other die being collinear with the tangent to the tube-engaging surface of the block at a second point which is substantially diametrically disposed relative to said first point.

5. A machine as claimed in claim 4, in which two or more pairs of spool-supporting members are provided whereby a coil on one supporting member of one pair may be prepared for drawing while a coil is being drawn between the supporting members of another pair.

6. A machine as claimed in claim 4 or 5, in which each 1,178,331 4/1916 Marvin 72281 supporting member is arranged for reciprocation in a verti- 2,704,151 3/ 1955 Holbrook 72277 cal direction.

References Cited CHARLES W. LANHAM, Primary Examiner UNITED STATES PATENTS 5 A. L. HAVIS, Assistant Examiner Re. 16,236 12/1925 Crosby 72281 420,165 1/1890 Morse 72277 US. Cl. X.R.

424,839 4/1890 White 72-281 72277, 281 

